The present invention relates to ink for ink jet recording suitable for ink jet recording, a process for preparing said ink, and ink cartridge and recording apparatus including said ink.
Up till now, as the ink used for ink jet recording, an ink comprising a dye serving as a colorant, a humectant, a penetrant and water has been well known. However, when forming images on a recording medium such as a recording paper with the ink that contains a water-soluble dye, there is a problem in the water-resistivity of the images. Specifically, when the images get wet with water, the dye contained in the ink dissolves out into water. In particular, when recording images on a plain paper (widely-commercialized papers particularly used for copy machines of electronic photograph type and not intended to provide optimum structure, composition, characteristics, etc. to papers purposed to use for ink jet recording), the water-resistivity of the images is so inferior.
Accordingly, as disclosed in Japanese Patent Laid-open Nos. 10-212439, 11-293167 and 11-315231, it has previously proposed to improve the water-resistivity of the images recorded on a recording medium by causing the ink to contain a hydrolyzable silane compound (an organic silicon compound) therein. Specifically, when the inks disclosed in the foresaid references are used, the ink in the form of droplets adheres onto a recording medium, followed by evaporation of water contained in the ink or penetration of the water into the recording medium, whereby the silane compound remained on the recording medium gives rise to a condensation and polymerization reaction, and then, the condensed and polymerized silane compound surrounds the molecules of the dye. Accordingly, the water-resistivity of the images is improved because, even though the images formed on the recording medium get wet with water, the dye molecules will never be dissolved out into water.
Since there has been no distinctive guide as to the content of the silane compound in the ink, however, the silane compound having completed the condensation and polymerization reaction cannot sufficiently surround the dye molecules in the ink, and therefore, there has been a problem of difficulty in stably obtaining the water-resistivity improving effect with the silane compound.
Now, explanation is given on this problem with reference to FIGS. 10 and 11. FIG. 10 is a model view showing a state when the silane compound has completed the condensation and polymerization reaction after adhesion of the ink droplets onto the recording medium and evaporation of water contained in the ink. Note that, in FIG. 10, though the network structure 70 of the silane compound is illustrated as a two-dimensional structure, the silane compound is actually structured in a three-dimensional structure. As shown in FIG. 10, when a silicon atom 62 and oxygen atom 63 both in a silane compound are bonded with each other to form a substantially-uniform network structure 70 of a silane compound, all of the dye molecules 50 are surrounded by the network structure of the silane compound. Accordingly, the dye molecules 50 will never be dissolved out into water even though the images on the recording medium get wet with water.
However, the reaction of said silane compound is indeed not completed thoroughly and firmly, and it is considered that there are portions where the silicon atom 62 and the oxygen atom 63 have not bonded. Thus, it is considered that defective portions 70A are given in the network structure 70 of the silane compound. If the size of the defective portion 70A is larger than the size of the dye molecule 50, the dye molecule 50 supposed to be surrounded by the network structure 70 is dissolved out into water through the defective portion 70A when the images on the recording medium are getting wet with water.
The present invention is achieved in view of the above-mentioned conventional problems, and it is an object of the present invention to provide the ink for ink jet recording use that can stably exert excellent waterresisting characteristic, a process for preparing said ink, a cartridge including said ink and a recording apparatus including said ink.